Limits...
The MoS 2 Nanotubes with Defect-Controlled Electric Properties

View Article: PubMed Central - HTML - PubMed

ABSTRACT

We describe a two-step synthesis of pure multiwall MoS2 nanotubes with a high degree of homogeneity in size. The Mo6S4I6 nanowires grown directly from elements under temperature gradient conditions in hedgehog-like assemblies were used as precursor material. Transformation in argon-H2S/H2 mixture leads to the MoS2 nanotubes still grouped in hedgehog-like morphology. The described method enables a large-scale production of MoS2 nanotubes and their size control. X-ray diffraction, optical absorption and Raman spectroscopy, scanning electron microscopy with wave dispersive analysis, and transmission electron microscopy were used to characterize the starting Mo6S4I6 nanowires and the MoS2 nanotubes. The unit cell parameters of the Mo6S4I6 phase are proposed. Blue shift in optical absorbance and metallic behavior of MoS2 nanotubes in two-probe measurement are explained by a high defect concentration.

No MeSH data available.


a X-ray powder diffraction pattern (A) The starting material composed of Mo6S4I6 nanowires with traces of MoS2 (asterisk) and Mo6S2I8. The two indexed peaks are used for approximation of the unit cell of Mo6S4I6; (B) The final material is composed of pure multiwall MoS2 nanotubes. b Raman spectra: (A) Mo6S2I8 nanowires, (B) Mo6S4I6 nanowires; arrows point traces of MoS2; square dot (see also the inset) shows a position of the characteristic peak at 117 cm-1, (C) MoS2 nanotubes gained by sulfurization of Mo6S4I6 nanowires. c Optical absorption spectra: (A) Mo6S4I6 precursor nanowires; (B) MoS2 nanotubes; (C) MoS2 polycrystalline material (powder). All materials were dispersed in ethanol.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211322&req=5

Figure 2: a X-ray powder diffraction pattern (A) The starting material composed of Mo6S4I6 nanowires with traces of MoS2 (asterisk) and Mo6S2I8. The two indexed peaks are used for approximation of the unit cell of Mo6S4I6; (B) The final material is composed of pure multiwall MoS2 nanotubes. b Raman spectra: (A) Mo6S2I8 nanowires, (B) Mo6S4I6 nanowires; arrows point traces of MoS2; square dot (see also the inset) shows a position of the characteristic peak at 117 cm-1, (C) MoS2 nanotubes gained by sulfurization of Mo6S4I6 nanowires. c Optical absorption spectra: (A) Mo6S4I6 precursor nanowires; (B) MoS2 nanotubes; (C) MoS2 polycrystalline material (powder). All materials were dispersed in ethanol.

Mentions: Besides Mo6S4I6 nanowires, X-ray investigation of the starting material (Figure 2a-A) reveals the presence of the Mo6S2I8 and traces of MoS2. The (002) MoS2 peak is shown by an asterisk in spectrum (a), while other MoS2 peaks cannot be resolved. Due to nearly identical skeletal structures, most of the diffraction peaks of Mo6S4I6 and Mo6S2I8 nearly match, leading to a broadening of the peaks in addition to the size effect broadening. As an example, the peak at ~.817 nm is composed of two peaks situated at 0.816(1) nm and at 0.825(8) nm. The last one can be associated with the Mo6S2I8 (110) planes, while the first one was used for the approximation of the unknown unit cell of Mo6S4I6 nanowires. The symmetry of the TED pattern (Figure 1d) was utilized for assignation of the peak to the (200) planes of the Mo6S4I6. The peak positioned at 0.197 nm was associated with the (006) planes. Complete determination of the Mo6S4I6 structure needs further studies.


The MoS 2 Nanotubes with Defect-Controlled Electric Properties
a X-ray powder diffraction pattern (A) The starting material composed of Mo6S4I6 nanowires with traces of MoS2 (asterisk) and Mo6S2I8. The two indexed peaks are used for approximation of the unit cell of Mo6S4I6; (B) The final material is composed of pure multiwall MoS2 nanotubes. b Raman spectra: (A) Mo6S2I8 nanowires, (B) Mo6S4I6 nanowires; arrows point traces of MoS2; square dot (see also the inset) shows a position of the characteristic peak at 117 cm-1, (C) MoS2 nanotubes gained by sulfurization of Mo6S4I6 nanowires. c Optical absorption spectra: (A) Mo6S4I6 precursor nanowires; (B) MoS2 nanotubes; (C) MoS2 polycrystalline material (powder). All materials were dispersed in ethanol.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211322&req=5

Figure 2: a X-ray powder diffraction pattern (A) The starting material composed of Mo6S4I6 nanowires with traces of MoS2 (asterisk) and Mo6S2I8. The two indexed peaks are used for approximation of the unit cell of Mo6S4I6; (B) The final material is composed of pure multiwall MoS2 nanotubes. b Raman spectra: (A) Mo6S2I8 nanowires, (B) Mo6S4I6 nanowires; arrows point traces of MoS2; square dot (see also the inset) shows a position of the characteristic peak at 117 cm-1, (C) MoS2 nanotubes gained by sulfurization of Mo6S4I6 nanowires. c Optical absorption spectra: (A) Mo6S4I6 precursor nanowires; (B) MoS2 nanotubes; (C) MoS2 polycrystalline material (powder). All materials were dispersed in ethanol.
Mentions: Besides Mo6S4I6 nanowires, X-ray investigation of the starting material (Figure 2a-A) reveals the presence of the Mo6S2I8 and traces of MoS2. The (002) MoS2 peak is shown by an asterisk in spectrum (a), while other MoS2 peaks cannot be resolved. Due to nearly identical skeletal structures, most of the diffraction peaks of Mo6S4I6 and Mo6S2I8 nearly match, leading to a broadening of the peaks in addition to the size effect broadening. As an example, the peak at ~.817 nm is composed of two peaks situated at 0.816(1) nm and at 0.825(8) nm. The last one can be associated with the Mo6S2I8 (110) planes, while the first one was used for the approximation of the unknown unit cell of Mo6S4I6 nanowires. The symmetry of the TED pattern (Figure 1d) was utilized for assignation of the peak to the (200) planes of the Mo6S4I6. The peak positioned at 0.197 nm was associated with the (006) planes. Complete determination of the Mo6S4I6 structure needs further studies.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

We describe a two-step synthesis of pure multiwall MoS2 nanotubes with a high degree of homogeneity in size. The Mo6S4I6 nanowires grown directly from elements under temperature gradient conditions in hedgehog-like assemblies were used as precursor material. Transformation in argon-H2S/H2 mixture leads to the MoS2 nanotubes still grouped in hedgehog-like morphology. The described method enables a large-scale production of MoS2 nanotubes and their size control. X-ray diffraction, optical absorption and Raman spectroscopy, scanning electron microscopy with wave dispersive analysis, and transmission electron microscopy were used to characterize the starting Mo6S4I6 nanowires and the MoS2 nanotubes. The unit cell parameters of the Mo6S4I6 phase are proposed. Blue shift in optical absorbance and metallic behavior of MoS2 nanotubes in two-probe measurement are explained by a high defect concentration.

No MeSH data available.